1. Field of the Invention
The present invention relates, in general, to a damper for refrigerators and, more particularly, to a structural improvement in such a damper to effectively vaporize moisture drops, condensed on a higher temperature surface of a damper""s baffle due to a dewing phenomenon caused by a difference in temperature between opposite surfaces of the baffle, thus allowing the baffle to be almost free from freezing on the surface.
2. Description of the Prior Art
As well known to those skilled in the art, refrigerators are machines which are designed to supply cool air, formed through heat exchanging processes of evaporators, into freezing and fresh compartments, thus keeping food within the two compartments while freezing the food within the freezing compartment and maintaining the freshness of food within the fresh compartment for an expected period of time. In conventional refrigerators, the supply of cool air for the freezing and fresh compartments is automatically controlled in order to accomplish preset desired temperatures within the compartments. In order to accomplish such a cool air supply control during an operation of a refrigerator, a damper is installed within the refrigerator. That is, the supply of cool air for the freezing and fresh compartments in conventional refrigerators is automatically and repeatedly stopped and restarted under the control of a damper.
In conventional refrigerators, the damper is installed on the cool air passage for the fresh compartment. FIGS. 1 and 2 show the construction of a conventional damper used for controlling the supply of cool air for the fresh compartment in a refrigerator.
As shown in FIGS. 1 and 2, the damper 10 is installed on the cool air passage for the fresh compartment of the refrigerator and controls the cool air supply for the fresh compartment. The arrow in FIG. 2 designates the flow direction of cool air from an evaporator into the fresh compartment through the damper 10. That is, the cool air, formed through a heat exchanging process performed by the evaporator installed within a heat exchanger chamber defined at the rear of the fresh compartment, is supplied into the fresh compartment under the control of the damper 10.
The damper 10 of FIGS. 1 and 2 is disclosed in U.S. Pat. No. 5,876,014. In a detailed description, the above damper 10 comprises a frame 12 having a cool air passing hole 12a, with a baffle 14 being hinged to the frame 12 and controlling the cool air passing hole 12a. The above baffle 14 is rotatable relative to the frame 12 by the rotating force of a stepping motor 20 in opposite directions, thus selectively opening or closing the cool air passing hole 12a. 
In order to transmit the rotating force of the stepping motor 20 to the baffle 14, a gear transmission mechanism is provided in the damper 10 as follows. That is, a pinion gear 22 is fixed to the rotating shaft 20a of the stepping motor 20 and transmits the rotating force of the motor 20 to a sectoral gear 24. The above sectoral gear 24 is fixed to the rotating shaft P of the baffle 14, and so the rotating shaft P is rotatable in cooperation with a rotating action of the sectoral gear 24. The stepping motor 20 and the gear transmission mechanism constitutes a drive unit for the baffle 14. When the rotating shaft P is rotated by the rotating action of the sectoral gear 24, the baffle 14 is rotated from its closed position shown by the solid line in FIG. 2 to its open position shown by the phantom line in the drawing, thus opening the cool air passing hole 12a. 
However, such a conventional damper 10 is problematic as follows. That is, when the baffle 14 is kept in its closed position as shown by the solid line in FIG. 2, there is an undesirable difference in temperature between opposite surfaces of the baffle 14. The left-hand surface of the baffle 14 in the drawing directly faces the cool air discharged from the evaporator, and so said surface is lower in temperature than the right-hand surface of the baffle 14 facing the fresh compartment. That is, the right-hand surface of the baffle 14 is higher in temperature than the left-hand surface due to the temperature within the fresh compartment and is dampened due to moisture escaping from food kept in the fresh compartment.
Due to such a difference in temperature between opposite surfaces of the baffle 14, moisture is condensed and forms small drops on the right-hand surface of the baffle 14 facing the fresh compartment. Such small drops of moisture condensed on the surface of the baffle 14 are undesirably frozen particularly at the edge of the baffle 14 due to the cool air flowing on the baffle 14. The rotating shaft P of the baffle 14 in the conventional damper 10 may be thus easily frozen, and may fail to smoothly rotate the baffle 14.
Such a problem, experienced in the conventional damper, ill-affects the operational function of the damper and finally deteriorates the operational reliability of refrigerators. This reduces the market competitiveness of the refrigerators.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a damper for refrigerators, which is designed to allow the baffle, installed around a cool air passage for the fresh compartment of a refrigerator, to be free from freezing.
Another object of the present invention is to provide a damper for refrigerators, which gives an appropriate quantity of moisture to the cool air for the fresh compartment of a refrigerator, thus allowing food in the fresh compartment to maintain its moisture and freshness for a desired period of time.
In order to accomplish the above object, the primary embodiment of the present invention provides a damper for refrigerators, comprising: a frame installed in the cool air passage within a refrigerator and having a cool air passing hole; a baffle selectively opening or closing the air passing hole of the frame; a rotating shaft rotatably holding the baffle relative to the frame while being installed on the baffle at a position between upper and lower edges of the baffle; and a drive unit rotating the baffle relative to the frame.
In the above damper, the baffle is rotatable around the rotating shaft so as to selectively open or close the cool air passing hole of the frame while exposing moisture drops condensed on a surface thereof to cool air flowing through the cool air passage when the baffle is rotated to open the cooling air passing hole.
In addition, the drive unit comprises: a drive power source generating a rotating force for the baffle; and a gear transmission mechanism transmitting the rotating force of the drive power source to the baffle.
The second embodiment of this invention provides a damper for refrigerators, comprising: a frame installed in a cool air passage within a refrigerator and having a cool air passing hole; a baffle selectively opening or closing the air passing hole of the frame; a link extending from an edge of the baffle while forming an angle between the link and the baffle, thus holding the baffle, the link having a hinge pin at an outside end thereof; and a drive unit rotating the baffle relative to the frame.
In the above damper, the baffle is rotatable around the hinge pin so as to selectively open or close the cool air passing hole of the frame while exposing moisture drops condensed on a surface thereof to cool air flowing through the cool air passage when the baffle is rotated to open the cooling air passing hole.
On the other hand, the angle between the baffle and the link ranges from 90xc2x0 to 135xc2x0.
In the above damper, the drive unit comprises: a drive power source generating a rotating force for the baffle; and a gear transmission mechanism transmitting the rotating force of the drive power source to the baffle.
In the damper of this invention, the moisture drops, condensed on the higher temperature surface of the baffle due to a temperature difference between opposite surfaces of the baffle while the baffle is closed, are fully exposed to the dry cool air when the baffle is opened. It is thus possible for the moisture drops to be quickly evaporated and absorbed by the dry cool air. The damper thus effectively prevents the baffle from freezing due to the condensed moisture drops and allows the baffle to be smoothly operated without failure. This finally improves the operational reliability of the damper and refrigerators.